Compression

 

Compression are files that sometimes need to be compressed to make the file size smaller. There are two ways in which techniques when it comes to compressing files, Lossless and Lossy.

Lossless Compressions

Lossless compressions are generally based on redundancy by reducing the file by encoding the file however not loosing anything in the process. Lossless is like Zip filing, Zip files is an example of a lossless compression. When unzipped the file becomes reconstructed.

The key point to grasp about lossless compression is that no information is irretrievably lost in the process. The common .zip format is an example of lossless compression, if used to ‘zip' a collection of text documents, the exact same documents will be reconstructed once ‘unzipped'
 

Lossy Compressions

Unlike lossless compression, lossy compression can cut the file size down much more; up to 3 quarters of the original file size can be compressed. However information is lost in the process. 

 

Lossy compressions are based on irrelevancy reduction strategies but will usually also employ some redundancy strategies. Lossy compressions transform and simplify the media information in a way that gives much larger reductions in file size than lossless compressions. A typical lossless compression can be expected to cut file sizes down to three quarters or two thirds of the original - perhaps even by half, if very efficient. In contrast, a lossy compression can reduce the file size to as little as 1% of the original, although anything less than 10% is likely to distort the file's content. The trade off, however, is that a lossy compression is by definition irreversible - it permanently disposes of information.